Start with the power supply and connections

A computer that won't turn on usually stops at the power stage before anything else happens. The first thing to check is whether power is actually reaching the machine. Look at the back of your computer where the power cable plugs in — make sure it is firmly seated in both the wall outlet and the computer itself. If the cable is loose, push it in until you hear or feel a click.

Next, check the wall outlet itself. Plug a lamp or phone charger into the same outlet to see if it works. If nothing powers on in that outlet, try a different one nearby. If the outlet is dead, you may have tripped a circuit breaker — go to your electrical panel and look for any switches in the "off" position, then flip them back to "on". If an outlet repeatedly dies when you plug your computer in, stop using it and call an electrician, because that suggests a wiring problem.

If the outlet works but your computer still does not turn on, inspect the power cable itself for damage — look for cuts, burns, or exposed wires. A damaged cable should be replaced, not repaired. You can buy a replacement power cable at any electronics store for $15 to $40.

Key Takeaways

  • Check that the power cable is fully plugged into both the wall outlet and the back of your computer, because a loose connection is the most common reason a computer appears dead.
  • Test the wall outlet with another device to confirm power is reaching it, and check your circuit breaker if the outlet is completely dead.
  • Look for physical damage to the power cable, and replace it if you see cuts, burns, or exposed wires.
  • If the power light comes on but nothing else happens, the problem is inside the computer and usually requires a technician to diagnose.
  • A computer that makes noise or shows lights but will not boot into Windows or Mac OS may have a software problem rather than a hardware failure.

Look for signs of power reaching the computer

Once you have confirmed the outlet works, look at the computer itself. Most computers have a small light on the front or back that turns on when power reaches them — this light may be green, blue, or amber depending on the model. If you see this light, power is getting to the machine. If you do not see any light at all, power is not reaching the computer's internal components.

Also listen for sound. When you press the power button, you should hear the fan start up within a second or two. If you hear nothing — no fan noise, no beeping, no clicking — the computer is not receiving power or the power button itself is broken. If you hear the fan start but the screen stays black, that is a different problem covered in the next section.

Some computers have a power button on the back as well as the front. Make sure the back button is in the "on" position. Older desktop computers in particular sometimes have a physical switch on the power supply itself — check that it is set to "on" (usually marked with a line rather than a circle).

Check the monitor and video connection

A computer that powers on but shows a black screen is often not broken — the monitor may straightforward be off, or the video cable may be loose. Press the power button on your monitor itself (not the computer). If the monitor has a light that turns on, you will know it is receiving power. If the monitor stays dark, plug it into a different outlet or test it with another computer if you have one available.

Next, check the cable that connects your monitor to the computer. On the back of your computer, locate the video port — this is usually a blue port labeled VGA, or a white port labeled HDMI, or a smaller port labeled DisplayPort or DVI. Make sure the cable is pushed firmly into this port. If the cable is loose, push it in until it clicks. If the cable is damaged or the port looks bent or broken, you will need to replace the cable or have the computer serviced.

If you have a laptop, the screen is built in and cannot be disconnected, so skip this step. If your laptop screen is black but you hear the fan running, the problem is likely inside the computer and requires a technician.

Restart using safe mode or recovery options

If your computer powers on, the monitor works, but the screen shows an error message or gets stuck on a loading screen, the problem is usually software rather than hardware. Try a hard restart: hold down the power button for 10 seconds until the computer shuts off completely, then wait 30 seconds and press the power button again to turn it back on.

If the computer still will not start normally, you may be able to boot into safe mode, which loads only the most basic drivers and programs. On a Windows computer, restart and repeatedly press the F8 key as the computer starts up — you should see a menu with "Safe Mode" as an option. On a Mac, restart and hold down the Shift key until you see the login screen. Safe mode can help you identify whether a recently installed program is causing the problem.

If safe mode does not work or you are not comfortable trying it, this is the point to contact a computer repair technician or the manufacturer's support line. They can walk you through more advanced troubleshooting or arrange a repair.

When to call a technician

If you have checked the power cable, tested the outlet, confirmed the monitor works, and the computer still will not turn on or start up, the problem is inside the computer itself. This could be a failed power supply, a problem with the motherboard, a failed hard drive, or another internal component. These are not repairs you should attempt yourself unless you have experience opening computers.

Contact the manufacturer's support line — you can usually find the number on their website or on the back of your computer. Have your computer's model number ready. They can often troubleshoot over the phone and may offer mail-in repair or direct you to an authorized repair center. If your computer is out of warranty, a local computer repair shop can diagnose the problem for a fee (usually $50 to $100) and give you a repair estimate.

If your computer is very old or the repair cost is high, you may decide it is more practical to replace it. But before you do, it is worth having a technician look at it — sometimes the problem is simpler than it appears.

Prevent future startup problems

Once your computer is working again, a few straightforward habits can reduce the chance of startup problems. Keep the area around your computer clean and dust-free, because dust buildup can cause fans to fail and components to overheat. Do not unplug the computer by pulling the power cable — always use the shutdown menu in Windows or Mac OS, then wait for the computer to fully power down before unplugging it. Sudden power loss can damage the hard drive or file system.

Use a surge protector power strip rather than plugging directly into the wall. Surge protectors cost $15 to $30 and protect your computer from voltage spikes that can damage the power supply or motherboard. If you live in an area with frequent power outages, consider a battery backup (called a UPS, or uninterruptible power supply), which keeps your computer running long enough to shut down safely.

Keep your operating system and drivers up to date by installing updates when Windows or Mac OS prompts you. Outdated software can cause startup problems. Restart your computer at least once a week — leaving it on continuously for months can cause overheating and memory issues that eventually prevent startup.

Frequently Asked Questions

My computer powers on but gets stuck on a black screen with a cursor. What do I do?

This usually means Windows or Mac OS is loading but taking longer than normal. Wait at least five minutes without touching anything — sometimes a first startup after an update takes a long time. If nothing changes after five minutes, try the hard restart method: hold the power button for 10 seconds, wait 30 seconds, then power on again.

The power light is on but the fan is not running. Is the computer broken?

Not necessarily. Some computers have fans that only spin when the processor gets hot, so the fan may not run when ready after startup. Wait a minute and listen again. If the fan never starts and the computer gets very hot to the touch, the cooling system may be blocked by dust — turn it off and use compressed air to clean the vents on the back and sides.

I see a blue screen with an error message. What does that mean?

A blue error screen (called a "blue screen of death" on Windows) usually means a hardware or driver problem. Write down the error code shown on the screen, then restart the computer. If the error returns, search the error code online or contact the manufacturer's support line with the code — it will help them diagnose the problem.

My laptop won't turn on and it is very hot. Should I keep trying?

No. Stop when ready and let it cool down for at least 30 minutes before trying again. Overheating can damage the battery and internal components. Once it cools, try powering on. If it overheats again quickly, do not use it — contact a repair technician, because the cooling system may be failing.

Can I fix a computer that won't turn on myself, or do I need a technician?

You can safely check the power cable, outlet, monitor connection, and try a hard restart. Anything beyond that — opening the computer, replacing internal parts, or advanced software troubleshooting — should be done by someone with experience. A wrong move inside the computer can cause more damage.